docstr: Tests whether the dataset_shard function works correctly for a single shard
  for the local worker.
docstr_tok: ["Tests","whether","the","dataset_shard","function","works","correctly","for","a","single","shard","for","the","local","worker","."]
code: def test_dataset_shard_with_only_local(self):
      """Tests whether the dataset_shard function works correctly for a single shard
      for the local worker."""
      config = AlgorithmConfig().offline_data(
          input_="dataset",
          input_config={"format": "json", "paths": self.dset_path},
      )
  
      # two ways of doing this:
  
      # we have no remote workers
      _, shards = get_dataset_and_shards(config, num_workers=0)
  
      assert len(shards) == 1
      assert isinstance(shards[0], ray.data.Dataset)
  
imports: import tempfile
  import os
  from pathlib import Path
  import unittest
  import pytest
  import ray
  from ray.rllib.algorithms.algorithm_config import AlgorithmConfig
  from ray.rllib.offline import IOContext
  from ray.rllib.offline.dataset_reader import DatasetReader, get_dataset_and_shards, _unzip_if_needed
label_desc: Use image node_id 4 for calling the TestDatasetReader obj's underlying member method code with example usage: obj.test_dataset_shard_with_only_local() without return types